linux-kernel - Re: [PATCH] remove the no longer needed pid_alive() check in __task_pid_nr

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Message-ID: <87mu74517d.fsf@x220.int.ebiederm.org>
Date:   Tue, 21 Apr 2020 10:05:10 -0500
From:   ebiederm@...ssion.com (Eric W. Biederman)
To:     Oleg Nesterov <oleg@...hat.com>
Cc:     linux-kernel@...r.kernel.org,
        Christof Meerwald <cmeerw@...erw.org>,
        Linux Containers <containers@...ts.linux-foundation.org>
Subject: Re: [PATCH] remove the no longer needed pid_alive() check in __task_pid_nr_ns()

Oleg Nesterov <oleg@...hat.com> writes:

> Starting from 2c4704756cab ("pids: Move the pgrp and session pid pointers
> from task_struct to signal_struct") __task_pid_nr_ns() doesn't dereference
> task->group_leader, we can remove the pid_alive() check.
>
> pid_nr_ns() has to check pid != NULL anyway, pid_alive() just adds the
> unnecessary confusion.
>
> Signed-off-by: Oleg Nesterov <oleg@...hat.com>
Reviewed-by: "Eric W. Biederman" <ebiederm@...ssion.com>

> ---

Good catch that does simplify things.

Eric

>  kernel/pid.c | 3 +--
>  1 file changed, 1 insertion(+), 2 deletions(-)
>
> diff --git a/kernel/pid.c b/kernel/pid.c
> index bc21c0fb26d8..47221db038e2 100644
> --- a/kernel/pid.c
> +++ b/kernel/pid.c
> @@ -475,8 +475,7 @@ pid_t __task_pid_nr_ns(struct task_struct *task, enum pid_type type,
>  	rcu_read_lock();
>  	if (!ns)
>  		ns = task_active_pid_ns(current);
> -	if (likely(pid_alive(task)))
> -		nr = pid_nr_ns(rcu_dereference(*task_pid_ptr(task, type)), ns);
> +	nr = pid_nr_ns(rcu_dereference(*task_pid_ptr(task, type)), ns);
>  	rcu_read_unlock();
>  
>  	return nr;